Emoji
already existed in documented (not to mention frequent) use when they were added to Unicode. As other commenters noted, the emoji originated in Japan and were encoded in the character sets used by mobile phones. Not adding them was not an option, because it would mean Unicode wouldn't be able to encode Japanese emails and text messages.
What happened in the past few years is that the emoji set was updated, because the Japanese core set missed symbols when considered from a global perspective. In some cases emoji have also been added pro-actively in cooperation with smartphone OS vendors; this is a point of contention, but I think it makes sense in this case.
> We end up with standard that is full of short lived symbols from 2000-2025 […]
That's fine. There is plenty of space in the Unicode standard. It also contains whole swaths of glyphs that were only used in some small country for a few decades, or that are obscure to the point of being almost irrelevant. But that is what Unicode is for. It is a means to encode the texts we produce as humans¹, not a proscriptive table of characters we ought to use.
1: Aliens too I guess, as long as they can provide proof of prior and significant enough use.